World leaders past and present will be in Berlin today for the 20th an niversary of the fall of communist repression’s most visible symbol: the 112-mile concrete wall that split the city for more than a quarter-century.

Conspicuously absent: the president of the United States, Barack Obama.

After all, it was one of his own supposed heroes, President John F. Kennedy, who famously flew to Berlin in 1963 and denounced the wall as “an affront to history” when he memorably proclaimed to all the world: “Ich bin ein Berliner.”

And it was another predecessor, Ronald Reagan, who even more famously stood before the heinous barrier and declared: “Mr. Gorbachev, tear down this wall!”

Less than two years later, the wall had tumbled.

But, then, Reagan — like JFK — viewed the Cold War as a defining battle between freedom and oppressive totalitarianism. And it was a war, he said, that the West, led by America, had to win.

For Reagan, that meant ongoing confrontation with what he rightly called “the Evil Empire.” By openly declaring that America would never allow the Soviet bloc to triumph, he paved the way for the collapse not only of the Berlin Wall but of communism itself.

It was also, he understood, the triumph of American exceptionalism, leadership and strength.

All of which runs counter to Obama’s view of America’s global role — and how to deal with adversaries.

For Obama, America is but one nation among many, no different — or more exceptional — than any other. Its record is one that, increasingly, he has felt compelled not to extol but to apologize for.

And, for this president, ideologies bent on America’s destruction must be met not with resistance but with rhetoric, outreach and “understanding.”

The Cold War, in this view, is an irrelevant historical relic — an example of American paranoia and fear-mongering prolonging a conflict that could have been resolved with warm-and-fuzzy speechmaking and the soft-pedaling of political differences.

Gone, it seems, are the days when America championed freedom, led by presidents whose oratory was matched by commitment and determined action.